Load measurement method and device

ABSTRACT

A device for axial load measurement on a mechanical control device having a rotating shaft may be used to derive a torque measurement. A mechanical control device may comprise a valve actuator for fluid flow control devices. The load measurement device may include a beam operatively connected to a rotatable shaft and configured to deform under axial displacement of the shaft. A sensor may be coupled with the at least one beam and configured to produce an output signal related to the axial displacement of the shaft. The beam may be retained between two bearings on the rotatable shaft at a first end, and fixed to a housing of the mechanical control device at a second end. The first end of the beam may displace axially with the rotatable shaft. The beam may comprise a discrete segment of a uniform width and thickness.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.12/224,746, filed Dec. 16, 2008, now U.S. Pat. No. 7,971,490, issued onJul. 5, 2011, the disclosure of which is hereby incorporated herein bythis reference in its entirety.

TECHNICAL FIELD

The present invention relates to a method and device for loadmeasurement, and, more specifically, to an axial load measurement on amechanical control device having a rotating shaft, for example, a valveactuator for fluid flow control devices. The load measurement may beused to derive a torque measurement.

BACKGROUND

Fluid flow control devices include devices for both liquids and gases.Valve actuators for fluid flow control devices are known and may bemechanically operated. For example, the valve actuator may be manuallydriven, operated by fluid pressure in which the shaft is connecteddirectly or indirectly to a fluid operated piston, or be driven by anelectro-hydraulic or electro-fluid means. Conventional valve actuatorscomprise an electrically driven input shaft, which may be rotatable atrelatively high speeds with relatively low torque. The input shaft may,through reducing gears such as a worm gear or a helical screw thread andnut, rotate a relatively high torque, low speed output shaft.

It may be desirable to determine the torque generated by the outputshaft. For example, when a valve is fully closed and seated, the torquerequired to open the valve may be considerably higher. Consistentlymonitoring the torque may indicate if a valve is wearing out orsticking. Trending patterns in the torque measurements may enablepredictive maintenance. Override shut-off features may be provided if atorque exceeds a predetermined allowable level.

Measurement of the axial force on the input shaft may be used todetermine the torque delivered by the output shaft. The axial loadmultiplied by the worm gear pitch radius is the torque delivered by theoutput shaft.

Conventional devices for measuring the end thrust or torque of arotating shaft are known and include a thrust-torque transducerdescribed in U.S. Pat. No. 4,182,168 to Desch. The thrust-torquetransducer includes a LVDT (Linear Voltage Differential Transformer)having a movable core axially aligned with, secured to, and rotatablewith the shaft, and producing an output signal corresponding to thrustor torque. However, in order to provide for operation of the transducerin both clockwise and counterclockwise rotations of the shaft, the Deschthrust-torque transducer requires presetting of a diaphragm of a thrustbearing. The Desch thrust-torque transducer does not detect anymisalignment of the axial load on the shaft.

Another conventional device for indicating loading on a shaft isdescribed in U.S. Pat. No. 5,503,045 to Riester. An increased load on aworm causes axial shifting of a worm shaft and an accompanyingdeformation of a membranous disc mounted on the worm shaft. One side ofthe disc is formed with a circumferentially extending, annular recess.The central portion of the disc is fixed against axial displacementrelative to the worm shaft by an axial bearing situated on one side ofthe disc and a bushing that is disposed on the opposite side of thedisc. A strain measuring strip on another side of the disc generateschanges in measurements with displacement of the worm shaft. The deviceof Riester does not provide a method for detection of any misalignmentof the load on the shaft.

Therefore, it would be advantageous to develop a technique for measuringthe torque generated by an output shaft using the axial displacement ofan input shaft, and detecting any misalignment of the load on the inputshaft.

DISCLOSURE OF THE INVENTION

The present invention, in a number of representative embodiments,provides a load measurement method and device that may be used todetermine a load including, but not limited to, the load on a rotatingshaft. A mechanical control device having a rotating shaft, for example,a valve actuator for fluid flow control devices, may include a loadmeasurement device of the present invention.

In accordance with one embodiment of the present invention, a mechanicalcontrol device includes a shaft configured for rotation, a beamoperatively connected to the shaft and configured to deform under axialdisplacement of the shaft, and a sensor coupled with the at least onebeam and configured to produce an output signal proportional to theaxial displacement of the shaft. The beam may have a substantiallyuniform cross-section through substantially its entire length.

The mechanical control device may additionally include bearings fortranslating the axial displacement of the shaft to the beam. Thebearings may include a first annular bearing disposed about the shaftand contacting a first surface of the beam, and a second annular bearingdisposed about the shaft and contacting a second, opposing surface ofthe beam. Additionally included in the mechanical control device may bean annular body encircling the shaft, with the beam extending outwardlyfrom the shaft toward the annular body. A portion of the beam may befixed to the annular body. A housing may be fixed to the annular body,and configured for axial movement of the shaft relative to the housing.

The output signal of the sensor of the mechanical control device mayidentify any misalignment of the worm shaft. The sensor may include atleast one strain gauge. The beam of the mechanical control device mayinclude a metal, and may also include an array of discrete beamsarranged in a spoke formation about the shaft.

In accordance with another embodiment of the present invention, a loadsensor for measuring the axial load on a rotatable shaft includes atleast one deflection beam having a first end portion thereof retainedbetween two bearings, each bearing operatively connected to therotatable shaft for translating axial movement of the shaft to the atleast one deflection beam (as a deflection), and a sensor operativelyconnected to the at least one deflection beam and configured formeasuring the deflection of the at least one deflection beam.

The sensor may comprise at least one strain gauge and the at least onedeflection beam may comprise a discrete metal segment having asubstantially uniform width and thickness therethrough. The at least onedeflection beam may include a second end portion fixed to a housing forthe load sensor, the housing being configured to enable relative axialdisplacement of the rotating shaft with respect thereto.

The load sensor may additionally include an annular body encircling therotatable shaft. The at least one deflection beam may include an arrayof deflection beams arranged in a spoke formation about the shaft,extending outwardly from the shaft toward the annular body, wherein asecond portion of each deflection beam is fixed to the annular body. Ahousing may be fixed to the annular body, the shaft being configured foraxial movement relative to the housing. Each deflection beam of thearray of deflection beams may include a sensor operatively connectedthereto, each sensor being in communication with an output device, whichrelates any misalignment of the worm shaft.

In yet another aspect, the present invention includes a method ofmeasuring a torque delivered to a valve. A rotatable shaft may includetwo bearings operatively coupled to the rotatable shaft. The methodincludes providing at least one beam disposed between the two bearingson a first end and coupled to a fixed housing on a second end, rotatinga worm gear with the shaft, the worm gear being operatively coupled witha worm wheel and shaft driving the valve, and transmitting the torquedelivered to the valve into axial movement of the rotatable shaft. Themethod additionally includes deflecting the at least one beam with theaxial movement of the shaft, which is translated to the beam with theaxial displacement of the two bearings, sensing the deflection of the atleast one beam, determining an axial load on the shaft using thedeflection of the at least one beam, and determining the torquedelivered to a valve using the axial load on the shaft and a radius ofthe worm gear.

In particular embodiments of the invention, providing at least one beammay comprise providing a beam of a substantially uniform width andthickness therethrough, or alternatively may comprise providing an arrayof beams arranged in a spoke formation about the rotatable shaft.Sensing the deflection of the at least one beam may compriseindependently sensing the deflection of each beam of the array of beams.

The features, advantages, and alternative aspects of the presentinvention will be apparent to those skilled in the art from aconsideration of the following detailed description taken in combinationwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming that which is regarded as the present invention,the advantages of this invention can be more readily ascertained fromthe following description of the invention when read in conjunction withthe accompanying drawings in which:

FIG. 1A is a cross-sectional view of a mechanical control device andtorque measurement device of the present invention;

FIG. 1B is a perspective view of the mechanical control device andtorque measurement device of FIG. 1A

FIG. 2 is a view of one embodiment of a plate of a torque measurementdevice of the present invention;

FIG. 3 is a view of another embodiment of a plate of a torquemeasurement device of the present invention;

FIG. 4 is a perspective view of the plate of FIG. 3 installed in arepresentative load measurement device of the present invention;

FIG. 5 is a perspective view of another embodiment of a load measurementdevice of the present invention; and

FIG. 6 is a view of yet another embodiment of a plate of a torquemeasurement device of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Although the foregoing description contains many specifics, these shouldnot be construed as limiting the scope of the present invention, butmerely as providing illustrations of some representative embodiments.Similarly, other embodiments of the invention may be devised that do notdepart from the spirit or scope of the present invention. Features fromdifferent embodiments may be employed in combination. The scope of theinvention is, therefore, indicated and limited only by the appendedclaims and their legal equivalents, rather than by the foregoingdescription. All additions, deletions, and modifications to theinvention, as disclosed herein, which fall within the meaning and scopeof the claims, are to be embraced thereby.

FIG. 1A illustrates a cross-section of an embodiment of a mechanicalcontrol device 10 including a torque measuring device 20 of the presentinvention. The mechanical control device 10 may comprise a valveactuator and may be operated, by way of example, manually, by a motor,or by fluid pressure. The mechanical control device 10 comprises a rotor150, which drives the worm shaft 30 coupled to a worm gear 40. The wormgear 40 drives and is operatively connected to an output shaft 45. Asthe worm shaft 30 is rotated to drive the worm gear 40, the forcerequired to drive the worm gear 40 and output shaft 45 may cause anaxial displacement of the worm shaft 30 relative to a housing 120 of themechanical control device 10. The axial movement may be registered witha plate 60. A portion of the plate 60 may be fixed to the housing 120,preventing axial movement thereof Another portion of the plate 60 maydeflect with the axial displacement of the worm shaft 30, transferred bya ball bearing 74, 76.

The deflection of the plate 60 may cause a significant strain therein,which may, in turn, be measured using a sensor 80 (see FIG. 2). Thesensor 80 may have an output that may be translated into the axial loadon the worm shaft 30. The axial load, when multiplied by the worm gearpitch radius, is the torque delivered by the worm gear 40 to the outputshaft 45. The axial movement of the worm shaft 30 may occur in eitherdirection, depending on the direction of rotation of the worm shaft 30and subsequent rotation of the output shaft 45. An output device 170 maybe provided to display information such as, by way of example, thestrain of the plate 60, the axial load of the worm shaft 30, and/or thetorque on the output shaft 45.

The worm shaft 30 shown in FIG. 1A rotates within a sleeve 90 onbearings 70, 74, and 76, which, by way of example, can include ballbearings. A perspective view is shown in FIG. 1B. Driving the worm gear40, which in turn drives the output shaft 45, applies an axial load onthe worm shaft 30. The axial load forces the worm shaft 30 to displaceaxially. The worm shaft 30 may be displaced in two opposing axialdirections, shown by arrows 1 and 2, and the plate 60 may be deflectedtoward two different positions. During rotation, the worm shaft 30 maybe displaced to the left, as shown by arrow 1. The axial load may betransferred to the plate 60 via the rotor 150. An attachment element 140secures the worm shaft 30 to the rotor 150. The attachment element 140may comprise, for example, a bolt or a screw. The worm shaft 30 pulls onthe attachment element 140. The attachment element 140 causes the rotor150 to axially displace with the worm shaft 30 and the rotor 150 pressesagainst the bearing 76. The bearing 76 pushes on the plate 60, causingthe plate to deflect toward a first flexed position. An inner race 76 aof the bearing 76 is flush with, and rotates with, the worm shaft 30. Anouter race 76 b of the bearing 76 contacts and pushes on the plate 60.The plate 60 does not rotate since the outer circumference of the plate60 is fixed to the housing 120 with attachment elements 130. A sensor 80may determine the strain on the plate 60 to determine the axial load onthe worm shaft 30.

Alternatively, the worm shaft 30 may rotate in the opposite direction,turning the output shaft 45 in the opposite direction. The worm shaft 30is thus axially loaded to the right, in the direction of arrow 2. Theworm shaft 30 is displaced to the right and a shoulder 100 of the wormshaft 30 may press against the bearing 70. The shoulder 100 comprises aradial face of the worm shaft 30 at a junction of a portion of the wormshaft 30 having a smaller diameter and a portion of the worm shaft 30having a larger diameter. The bearing 70 presses against the sleeve 90,causing matching axial displacement of the worm shaft 30 and the sleeve90. The sleeve 90 and the bearing 74 thus undergo substantially the sameaxial displacement as the worm shaft 30, forcing the bearing 74 againstthe plate 60, and causing the plate to deflect toward the second flexedposition. An inner race 74 a of the bearing 74 is flush with, androtates with, the worm shaft 30. An outer race 74 b of the bearing 74contacts the sleeve 90 and the plate 60, transmitting the axial loadthereto. The first flexed position of the plate 60 may correspond to aclosing force being applied to the valve (not shown) via the mechanicalcontrol device 10, and the second flexed position may correspond to anopening force being applied to the valve, or vice versa, depending onthe direction of the threads of the worm shaft 30 and the configurationof the valve in communication with the valve actuator.

The sleeve 90, as depicted, does not rotate with the worm shaft 30.However, it is understood that a sleeve that rotates in conjunction withthe worm shaft 30 is within the scope of the present invention. Inaddition, it is within the scope of the present invention to include asecond sleeve about the worm shaft 30, between the rotor 150 and thebearing 76. Thus, a sleeve (and not the rotor 150) may transmit theaxial load to the plate 60 from the worm shaft 30 when experiencing anapplied load in the direction of arrow 1.

An axial bearing may be positioned between the rotor 150 and the deviceoperating the mechanical control device 10, such as a motor, enablingthe rotor 150 to move axially relative to the operating device. Thus,any outside axial forces on the operating device may also be absorbedwith the axial bearing and do not affect the measurement of the axialload.

FIG. 2 depicts a plate 60 a according to a particular embodiment of thepresent invention. The plate 60 a is substantially planar, comprising anannular body 62 a and an array of four discrete inwardly protrudingbeams 65 a. Each beam 65 a may have a substantially rectangularcross-section may be disposed at a right angle to each adjacent beam 65a. The annular body 62 a and the inwardly protruding beams 65 a may becontiguous, formed from a single piece of material, such as, forexample, a metal disc. For example, the plate 60 a may be formed bystamping, forging, or laser cutting. Alternatively, the beams 65 a maybe attached to the annular body 62 a, such as with an adhesive or anattachment element. The beams 65 a may be formed of the same material asthe annular body 62 a or can be formed from a different material. By wayof example, suitable materials for the annular body 62 a and beams 65 ainclude a metal, such as copper, aluminum, steel, stainless steel, or apolymer. The inwardly protruding beams 65 a may be removable andreplaceable.

The inwardly protruding beams 65 a provide a passageway 110 for the wormshaft 30 (not shown in FIG. 2) to extend therethrough. The inwardlyprotruding beams 65 a may be arranged in a spoke formation within thecentral opening of the annular body 62 a. However, the beams 65 a neednot join at the center of the annular body 62 a central opening; rather,the center may comprise the open passageway 110. The ends of the beams65 a distal from the annular body 62 a are free to displace under theload of the axial displacement of the worm shaft 30, transferred by thebearings 74, 76. (See FIG. 1A.) Each beam 65 a may have a substantiallyuniform thickness t and width w along the length 1 of the beam 65 a.

FIG. 2 depicts (with shading) the strain under deflection on the annularbody 62 a and each beam 65 a of the plate 60 a. The darkly shadedportions represent the portions under the greatest strain, and thelighter shaded areas show the portions under less strain. The plate 60 ais depicted with four apertures 50 through the annular body 62 a,enabling the plate 60 a to be secured to a housing 120 (see FIG. 1A) ofthe mechanical control device 10. Attachment elements 130, for example,bolts, pins, or screws, may be used to secure the plate 60 a. The plate60 a may be secured by methods other than attachment elements, such as,for example, by brazing or welding.

During use, the motor may turn the worm shaft 30, which rotates theoutput shaft 45. The force causing the output shaft 45 to turn causes anaxial movement of the worm shaft 30. The sleeve 90 on the worm shaft 30also moves axially, pushing the bearings 74 against each beam 65 a ofthe array. Each beam 65 a flexes with the portion of the beam 65 a thatis in contact with the bearing being displaced with the axial movementof the shaft. The annular body 62 a of the plate 60 a is fixed to thehousing and is not displaced. Thus, each beam 65 a deflects or flexes,causing a strain therein. The strain within each beam 65 a may bemeasured using a sensor 80. Each beam 65 a may include a sensor 80 or,alternatively, only one beam may include a sensor 80.

Including a sensor 80 on a plurality of beams 65 a of the array of beamsenables independent measurements of the stress and/or strain on each ofthe plurality of beams 65 a. Each beam 65 a of the array of beams 65 ais discrete and the array may surround the worm shaft 30. Each beam 65 amay undergo the axial displacement of the worm shaft 30 at separatelocations about the circumference of the worm shaft 30. Thus, if theworm shaft 30 bends or assumes any other misalignment of the axial load,the sensors 80 on each beam 65 a may sense different measurements.Comparing the measurements further enables a determination of anymisalignment of the axial load on the worm shaft 30. The sensors may beconfigured to cancel out any misalignment and to provide a signalcorresponding to a reading incorporating any misalignment.Alternatively, a separate signal may be provided, warning of themisalignment.

FIG. 3 depicts another embodiment of a plate 60 b according to thepresent invention. The plate 60 b comprises a substantially planarannular body 62 b having four discrete inwardly protruding beams 65 b.Each beam 65 b may have a substantially rectangular cross-section andmay be disposed at a right angle to each adjacent beam 65 b. Corners 66b at the junction of the annular body 62 b and inwardly protruding beams65 b are chamfered. The chamfering may reduce the stress on the plate 60b at the corners 66 b. The inwardly protruding beams provide apassageway 110 for the worm shaft 30 (not shown in FIG. 3) to extendtherethrough. The plate 60 b shows the stress under deflection of theannular body 62 b and each beam 65 b with shading. The darkly shadedportions represent the portions under the greatest stress, and thelightly shaded area shows the portions under less stress. The plate 60 bis depicted with four apertures 50, enabling the plate 60 b to besecured to a housing 120 (see FIG. 1A) of the mechanical control device10. Attachment elements 130, for example, bolts or screws, may be usedto secure the plate 60 b.

FIG. 4 is a perspective view of the plate of FIG. 3 installed in a loadmeasurement device 20 b of the present invention. The rotor 150protrudes from the center of the plate 60 b. A portion of the worm shaft30 is encased within the rotor 150 and secured thereto with attachmentelement 140. The bearing 76 encircles the worm shaft 30. A distal end ofthe rotor abuts the bearing 76, transmitting any axial load in thedirection of arrow 1 (see FIG. 1A) thereto. The outside race 76 b of thebearing contacts the surface of each beam 65 b on a first portion distalfrom the annular body 62 b. Each beam 65 b may include a second portionsecured to the annular body 62 b, which does not undergo displacementsince the annular body 62 b is fixed to the housing 120. The firstportions of the beams 65 b displace with the bearing 76, while thesecond portions of the beams 65 b are secured to the fixed annular body62 b. Thus, the beams 65 b deflect or flex, which places the beam undera strain. The strain may be measured with a sensor 80, such as a straingage.

FIG. 5 is a perspective view of a load measurement device 20 c accordingto a particular embodiment of the invention. Plate 60 c comprises anarray of three discrete beams 65 c disposed in a spaced-apartconfiguration, each beam 65 c extending outwardly from the worm shaft30. Although the present embodiment is shown with three beams 65 c, itis understood that any number of beams 65 c can be used. Each discretebeam may be secured to the housing 120 with an attachment element 160.Each beam 65 c may have a sensor 80 mounted thereon or, alternatively,only one or two of the beams 65 c may include a sensor 80. The sensor 80may include a plurality of sensors disposed in a plurality of locationson the beam 65 c. In one embodiment, the sensors 80 may be located inthe areas of maximum strain. The beams 65 c do not contact the wormshaft 30, however, any axial load applied to the worm shaft 30 may betransferred to the beams 65 c via the bearing 74. The beams 65 c do notcompletely encircle the worm shaft 30, rather, each beam 65 c isseparately spaced.

The beams 65 c need not be secured to an annular body, such as the beams65 a and 65 b depicted in FIGS. 3, 4, and 5. The beams 65 c may eachcomprise an elongated body, having a substantially uniform cross-sectiontherethrough. A first portion of each beam 65 c may be free to axiallydisplace with the worm shaft 30, under the axial load transferred bybearing 74. A second portion of each beam 65 c, at an opposite endlongitudinally from the first portion, may be secured to the housing 120with an attachment element 160. The worm shaft 30 may be axiallydisplaced relative to the housing 120 under the axial load. The firstportion of each beam 65 c may be displaced relative to the housing 120with the worm shaft 30. The second portion of each beam 65 c can besecured to the housing and can be prevented from being displaced. Thus,each beam 65 c may deflect, causing strain therein. The strain may bemeasured with the sensor 80.

A plate 60 may include any number of beams 65 a-65 c. For example, theplate 60 b depicted in FIG. 4 includes an array of four beams 65 b, andthe plate 60 c depicted in FIG. 5 includes an array of three beams 65 c.Additionally, a plate having only a single beam is within the scope ofthe present invention.

Measuring the direct reaction forces on internal components of amechanical control device, such as the axial load on a worm shaft 30, isan accurate method of determining the torque that the mechanical controldevice is delivering to an output shaft. This measurement is independentof gear efficiency, gear speed, motor torque, and motor applied linepower. A beam 65 a, 65 b, 65 c of a load measurement device 20, 20 b, 20c of the present invention may be formed so that the deflection causedby the axial load on the worm shaft 30 creates enough strain to obtainan electronic signal with the sensor 80, but not enough to cause apermanent strain or deflection to the beam 65 a, 65 b, 65 c. The wormgear 40, driven by the worm shaft 30, may be a shell type or may beintegral to the worm shaft 30.

FIG. 6 depicts a plate 60 d according to a particular embodiment of thepresent invention. The plate 60 d is annular, having a passageway 110 dfor the worm shaft 30 (not shown in FIG. 6) to extend therethrough. Theannular plate 60 d may be contiguous, formed from a single piece ofmaterial, such as, for example, a metal disc. For example, the plate 60d may be formed by stamping, forging, or laser cutting. By way ofexample, suitable materials for the plate 60 d include a metal, such ascopper, aluminum, steel, stainless steel or a polymer. The plate 60 dmay include apertures 50 therethrough, enabling the plate 60 d to besecured to a housing 120 (see FIG. 1A) of the mechanical control device10. A sensor 80 may be positioned in an area of maximum strain on theplate 60 d, near an aperture 80.

Although the foregoing description contains many specifics, these arenot to be construed as limiting the scope of the present invention, butmerely as providing certain representative embodiments. Similarly, otherembodiments of the invention can be devised which do not depart from thespirit or scope of the present invention. The scope of the invention is,therefore, indicated and limited only by the appended claims and theirlegal equivalents, rather than by the foregoing description. Alladditions, deletions, and modifications to the invention, as disclosedherein, which fall within the meaning and scope of the claims, areencompassed by the present invention.

What is claimed is:
 1. A method of measuring a torque delivered to avalve, comprising: providing a rotatable shaft having two bearingsoperatively coupled thereto; providing at least one beam disposedbetween the two bearings on a first end and coupled to a fixed housingon a second end; rotating a worm gear with the shaft, the worm gearoperatively coupled with a worm wheel and shaft driving the valve;transmitting the torque delivered to the valve into axial movement ofthe rotatable shaft; sensing deflection of the at least one beam due toaxial displacement of the two bearings and axial movement of the shaft;determining an axial load on the shaft using the deflection of the atleast one beam; and determining the torque delivered to a valve usingthe axial load on the shaft and a radius of the worm gear.
 2. The methodof claim 1, wherein providing at least one beam comprises providing abeam of a substantially uniform width and thickness therethrough.
 3. Themethod of claim 1, wherein providing at least one beam comprisesproviding an array of beams arranged in a spoke formation about therotatable shaft.
 4. The method of claim 3, wherein sensing thedeflection of the at least one beam comprises independently sensing thedeflection of each beam of the array of beams.
 5. A method of measuringaxial load comprising: providing a rotatable shaft; providing at leastone deflection beam disposed between the two bearings on a first end andcoupled to a fixed housing on a second end, each bearing operativelyconnected to the rotatable shaft; rotating the shaft; translating axialmovement of the shaft to a deflection of the at least one deflectionbeam; providing a sensor operatively connected to the at least onedeflection beam; measuring the deflection of the at least one deflectionbeam; and determining an axial load on the shaft using the deflection ofthe at least one beam.
 6. The method of claim 5, wherein providing atleast one deflection beam comprises providing a beam of a substantiallyuniform width and thickness therethrough.
 7. The method of claim 5,wherein providing at least one deflection beam comprises providing anarray of beams arranged in a spoke formation about the rotatable shaft.8. The method of claim 7, wherein sensing the deflection of the at leastone deflection beam comprises independently measuring the deflection ofeach beam of the array of beams.
 9. The method of claim 5, wherein thesensor comprises at least one strain gauge.
 10. The method of claim 5,wherein the at least one deflection beam comprises a discrete segment ofa substantially uniform width and thickness therethrough.
 11. The methodof claim 5, wherein the at least one deflection beam comprises a metal.12. The method of claim 5, wherein the at least one deflection beamincludes a second end portion fixed to a housing for the load sensor,the housing configured to enable relative axial displacement of therotating shaft with respect thereto.
 13. A method of measuring axialload comprising: providing a shaft configured for rotation; providing anannular plate operatively connected to the shaft and configured todeflect under axial displacement of the shaft, wherein the shaft extendsthrough a central passageway of the annular plate; rotating the shaft;providing a sensor operatively connected to the annular plate; measuringthe displacement of the annular plate; and determining an axial load onthe shaft using the displacement of the annular plate.
 14. The method ofclaim 13, further comprising: providing at least one circumferentiallypositioned aperture through the annular plate.
 15. The method of claim13, wherein the sensor is positioned on the annular plate radiallybetween the central passageway and the at least one circumferentiallypositioned aperture.
 16. The method of claim 13, further comprisingdeflecting at least one inwardly protruding beam of the annular plateposition in the central passageway of the annular plate by displacingthe shaft.